Removable pressure-sensitive adhesives are used on a variety of products including labels, tapes and the like to enable the product to adhere to a substrate and then later be removed from the substrate without difficulty and without leaving a stain or residue. To be suitable for such applications, the pressure-sensitive adhesive must have good adhesion with low peel strength and must not exhibit a significant increase in adhesion over time. Optimally, the pressure-sensitive adhesive should exhibit such physical properties on a variety of substrates.
One commercially available removable pressure-sensitive adhesive is an acrylic emulsion polymer which has poor mandrel performance and exhibits excessive adhesion buildup on some substrates over time. The product also performs only at a narrow coat weight range of 18 to 20g/m.sup.2 and tends to be expensive.
Another commercially available removable pressure-sensitive adhesive is a formulated rubber composition which, over time, tends to phase separate. This results in edge ooze, face bleed and, on some substrates, excessive adhesion buildup. This formulation can only be coated at low speeds and the convertibility is poor.
One attempt to improve the performance of removable pressure-sensitive adhesives formed by acrylic emulsions involved the blending of two commercial polymers mixed with fillers and ionic crosslinkering agents. This formulation, however, suffered from incompatibility as shown by two different glass transition temperatures. In addition, the adhesive left stains on certain substrates.
Accordingly, there is a need for a removable pressure sensitive adhesive which demonstrates good adhesion and removability properties over a long period of time and on a wide variety of substrates.